1, 2. Extemporaneous (extempore ), impromptu,improvised are used of expression given without preparation or only partial preparation. Extemporaneous and impromptu may both refer to speeches given without any preparation: an extemporaneous (impromptu ) speech.Extemporaneous may also refer to a speech given from notes or an outline: extemporaneous lectures.Impromptu also refers to poems, songs, etc., delivered without preparation and at a moment's notice. Improvised is applied to something composed (recited, sung, acted), at least in part, as one goes along: an improvised piano accompaniment.